Heat treatment of shafts and the like



May 28, 1940. F. s. DENNEEN ET AL HEAT TREATMENT OF SHAFTS AND THE LIKE Filed Dec. 14, 1935 INVENTOR.

Patented May 28, 19510 UNITED STATES PATENT oFFics azoavse HEAT TREATMENT OF SHAFTS AND THE LIKE corporation of Ohie Application December 14, 1935, Serial No. 54,388

8 Claims.

The present application is directed to the hardening of shafts and the like which are of considerable length.

The input required to heat a long shaft in one operation is too great to be economically enrployed and for this reason we have developed the present invention, by which successive increments of the shaft may be heated which, at the completion of the operation will result in a hardened surface over as much of the length as desired.

It is frequently desirable to provide different hardness characteristics at different point on such a shaft. For instance, it may be desirable to harden one portion of the shaft deeper than another part or it maybe desirable to leave a por tion of the shaft untreated. By providing controls to govern the rate of movement of the article and inductor with respect to each other and to control the input and the application of quenching fluid, it is possible to attain any desired combination needed. As will be hereinafter described, the heating cycle, the quenching cycle and the rate of movement of the article with re spect to the inductor are all synchronized with each other.

To the accomplishment of the foregoing and. related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims; the following description and the annexed drawing setting forth in detail certain mechanism embodying the invention, such disclosed means constituting, however, but one of various mechanical means in which the principle of the invention may be used.

In said annexed drawing:

Fig. l is a schematic diagram of our apparatus showing a shaft in process of being heat treated therewith; and Fig. 2 illustrates a shaft which may be hollow or tubular having hardened zones provided by our process.

Referring now to Fig. i, the shaft 5 is equipped with eye members 6 and l, these eye members being held in position by the guides 8 and 9 but being capable of sliding action in those guides. An inductor ring H3, preferably hollow and with means for water cooling, is connected to an alternating current source, preferably high fre-- quency, so that when the high frequency current is supplied to the inductor ring, heating is set up at a high rate in that portion of the mrface of the shaft embraced by the inductor. A hollow quenching ring I I is placed just below the induc-= tor so that as the shaft is drawn downward through the inductor and through the quenching ring, quenching fluid is directed against the heated surface through openings l2 in the quenching ring thereby cooling and hardening the surface progressively as the piece is fed through the apparatus. A shield it prevents the quenching fluid from working up within the heating inductor.

Suitable flexible cables id and i5, secured to the eye members pass over the pulleys ii and 58, cable i4 being wrapped one or more times around the pulley iii so that when pulley it is driven it will cause cable ii to travel, thereby giving the necessary travel to the shaft 5. The other ends of cables hi and it are attached to corresponding ends of the rack carrying member it, this rack bar being suitably held in position by the guides and 2i and traveling in a way to correspond with the travel of the shaft 5 but in the opposite direction, however. A turnbuckle 23 serves for adjusting the tension in the cables.

A motor 25 connected by suitable shaft and gearing, notshown, to the pulley it drives that pulley, thereby giving the desired travel to the shaft 5 and the rack bar it. The motor is is preferably a direct current, variable speed type, and is supplied with current through the leads 2%). Attached to the rack bar is rack 22 engaging a pinion 26 which drives a cam ii. A cam follower 28 rides against cam 2i and is held in contact therewith and made to follow the cam contour by spring or other suitable means. Attached to the cam follower and suitably insulated therefrom is a conducting member 2a arranged so that in its varying positions it will short circuit or cut out sections of the resistance 38 that is placed in series with the field 35 of the variable speed motor 24 By giving the cam 2? the proper form, the field resistance of the variable speed motor 2 is changed in such a way as to vary the speed of the motor, thereby varying the rate of travel. of the cable It over the pulley it with corresponding varying speed of travel of shaft 5 through the inductor and quenching members. The rate of travel of the shaft 5 may therefore be varyingly controlled throughout the length of its travel through the apparatus, the travel obtainable being substantially at any rate that is found necessary or desirable.

Engaging the same rack 22 but at another position is a pinion 26 attached to and driving a cam 32. A cam follower 33 rides against cam 32 and is held in contact therewith and made to follow the cam contour by spring or other suitable means. A conductor member 34 attached to the cam follower 33 but insulated therefrom is made to travel by the cam 32 in such a way as to short circuit increments of the resistance 35 inserted in series with the field 36 of the high frequency generator 3?.

Depending upon the shape of the cam 32, the voltage of the generator ill is varied and thus the power applied any place along the shaft may be given substantially any desired value and the rate and depth of surface heating thereby controlled.

At another position on rack bar 99 a second rack 73% engages a pinion 39 attached to and driving a cam ill. Acarn follower ii engaging the cam id and held in contact therewith is made to follow the cam contour by spring or other suitable means, actuates a valve 13 through a lever 62 thereby controlling the quenching fluid delivered against the heated portion of the shaft 5 through the quenching ring ii. By suitably forming this earn contour, the quenching action may be varied and controlled as desired over the entire length of the surface quenched. Quenching fluid is supplied to the valve 33 through the connection dd. For certain purposes several cams controlling dilierent valves for the supply of different quenching media are attached to the same or other pinions and the quenching media delivered by these different valves is either all discharged through the same quenching ring or through separate rings or ring sections.

While our drawing shows a cylindrical type of shaft, obviously articles of a very wide variety of sections other than cylindrical can be heat treated in our apparatus.

in Fig. i we have shown the inductor connected to the secondary of a transformer. The primary d6 of that transformer is connected to the terminals of the high frequency generator through suitable switches, not shown. A condenser ll is connected across the terminals of the primary 56 for the purpose of power factor correction the circuit.

In 2 we show a typical shaft that has been heat-treated in the apparatus illustrated in l. The shaded lines indicate the depth of the hardened zone along the shaft. The figures marked on the drawing at different points along the shaft indicate hardness in varying degree (as measured by Brinell hardness testing machine) obtainable along the shaft at substantially the positions indicated and by our apparatus method. With the apparatus shown in Fig. and method described herein the h ating energy input in the surface zones of the shaft may be varied at will along the entire length of the shaft. The rate of travel of the shaft through the heating inductor may be varied at will throughout the length of travel of the shaft. The duration and intensity of the quenching action may be varied at will at any point along the travel of the shaft.

With the current source of suitably high frequency and with a sufiiciently high power input to the inductor, the surface of the shaft may be heated to quenching temperature so fast that sub stantially no heat will penetrate appreciably below the depth it is desired to harden. Immediate and vigorous quenching of the surface after it has been brought to proper quenching tempera ture will give substantially the maximum surface hardness that is obtainable by heating and quenching the particular material in. use. If, however, the flow oi coolant is reduced or interrupted before the heated part has been thoroughly cooled, the heat in the layers underlying the part that has been cooled and hardened will travel outward, thereby tempering or softening the outer surface and reducing the hardness that had just been imparted by the initial quenching action.

Therefore the heating and quenching action and the resultant depth of hardness as well as degree of hardness along the shaft may readily be controlled to substantially any degree, through the apparatus shown in Fig. i and the method described herein. We have provided means to vary the intensity of the heating action, to vary the rate of travel of the piece through the heating inductor, and to vary the intensity and duration of the quenching action so that by a judicious adjustment or combination of these variable control features a shaft or article having substantially any desired physical characteristics (within the limits obtainable with the particular material in use), particularly in its surface zones, may be produced. I

Other modes of applying the principle of our invention may be employed instead oi the ones explained, change being made as regards the process or means herein disclosed for providing the product or modifications of the product described, provided the modes of applying the invention be those stated by any of the following claims or their equivalents.

We, therefore, particularly point out and distinctly claim as our invention:

1. In apparatus for surface hardening an article of the class described, a circumferentially extending inductor, means for supplying high frequency current to said inductor, means for moving the article longitudinally relative to the inductor and in proximity with the inductor, and means for controlling heating in a surface zone of the article, said last named means comprising cam means for varying the density of the inducing current and means for varying the rate of movement of the article, the last named means being controlled by a in position of the article.

2. apparatus for surface hardening an article oi the class described, a peripherally extendinductor, means for supplying current to said inductor, a quenching chamber adjacent to said inductor, means ior moving the article longituclinally relative to the inductor and in proximity with the inductor, means for controlling a varying flow of quenching fluid from said uuench-= ing chamber, said last named means comprising a valve being actuated by a control member, the control member being governed by a relative movement of the article and the inductor.

3. in a process for heat treating an article of the class described, the steps comprising passing a surface of the article progressively past an inductor and in close proximity therewith, causing high frequency current to how in said inductor whereby current is generated in a surface zone of the article, simultaneously varying the rate of movement oi the article and the current being delivered to the inductor whereby heating penetrates to varying depths in the article, projecting a quenching fluid onto the surface zone as the surface zone emerge from proximity with the inductor, and varying the rate of flow of quenching fluid to correspond with the varying depths of the heated zone.

In a process for heat treating an article of the class described, the steps comprising moving a surface zone of the article in heating proximity with an inductor, causing high frequency heating current to ilow in the inductor. varying the density of the current in the inductor while the rate of movement oi! the article is varied, and projecting a quenching medium onto the surface zone in varying quantities, the quantities of the quenching medium being controlled by a relative movement of the article and the inductor.

5. In apparatus for progressively heating successive increments of an elongated article by induction, a fixed support, a second support movable relative to said fixed support, said article carried by one support and an inductor carried by the other support and adapted to lie in spaced relation with the article, means to move the two supports relative to each other to bring successive increments of the article within the heating range of the inductor, a source of periodically varying current to supply said inductor and means controlled by relative movement between the supports to vary the electrical input to said inductor.

6. In apparatus for progressively heating successive increments of an elongated article by induction, a fixed support, a second support movable relative to said fixed support, said article carried by one support and an inductor carried by the other support and adapted to lie in spaced relation with the article, means to move the two supports relative to each other to bring successive increments of the article within the heating range of the inductor, a motor generator source of periodically varying current to supply said inductor including a generator field winding and means and said inductor.

controlled by relative movement between the supports to vary the electrical excitation of said field winding.

7. In apparatus for progressively heating successive increments of an elongated article by induction, a fixed support, a second support movable relative to said fixed support, said article carried by one support and an inductor carried by the other support and adapted to lie in spaced relation with the article, means to move the two supports relative to each other to bring successive increments of the article within the heating range of the inductor, quench means to quench a heated increment of said article and means controlled by relative movement between the supports to govern the application of quench to said article.

8. In apparatus for progressively heating successive increments of an elongated article by induction, a fixed support, a second support movable relative to said fixed support, said article carried by one support and an inductor carried by the other support and adapted to lie in spaced relation with the article, means to move the two supports relative to each other to bring successive increments of the article within the heating range of the inductor, and means controlled by relative movement between said article and said inductor to vary the rate of movement between said article WILLIAM C. DUNN.

FRANCIS S. DENNEEN. a 

